Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/78—Preparation processes
  • C08G63/82—Preparation processes characterised by the catalyst used
  • C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof

Definitions

• This invention is concerned with poly(ethylene terephthalate) resin and methods for making it.
• the resin is suitable for use in forming films and moulded articles such as bottles.
• This invention is especially concerned with increasing the crystallization time of poly(ethylene terephthalate) resin so as to give the user, when manufacturing a film or a moulded article, such as a bottle, therefrom more processing time, after the film or moulded article has been formed, before disadvantageous crystallization.
• Poly(ethylene terephthalate) can be either crystalline, in which case it is white and opaque, or amorphous, when it is generally clear and glossy and is less brittle than the crystalline form.
• the melt polymer is either extruded onto a casting roll or, if a moulded article is to be manufactured, a tubular slug is first formed from the resin and placed into a mould and the slug is then expanded to conform to the shape of the mould.
• Films or moulded articles are desirably transparent, white opaque films or bottles being commercially undesirable.
• British Patent 793,111 discloses the preparation of polyesters, and particularly poly(methylene terephthalate)s and poly(ethylene terephthalate)s, using an alkyl titanate to catalyze the ester inter- chanqe reaction and the subsequent polycondensation reaction whereby the polymer is prepared.
• This patent teaches that from 0.001% to 1.5% of the tetraalkyl titanate is used based on the original weight of dialkyl terephthalates used. There is no teaching about the problem of increasing the crystallization time of a poly(ethylene terephthalate) resin.
• U.S. Patent 4,131,601 discloses using s preformed titanate compound, obtained by reacting titanic acid ester with an aromatic ester, as a polycondensation catalyst in the preparation of polyesters.
• This patent teaches that although titanium compounds result in a very rapid rate of polycondensation-, they also give polyesters which have a distinctly yellow colour and a decreased softening point. A yellow colour, in a film or moulded article, would, in the main, be commercially unacceptable.
• the '601 patent is silent about the problem of time of crystallization of a poly(ethylene terephthalate) resin.
• U.S. Patent 2,822,348 is directed to ester interchange reactions and to the catalysis of these reactions.
• This patent discloses the use of an alkyl titanate catalyst for such ester interchange reaction. It is taught that the reaction, using the alkyl titanate ester, proceeds faster at lower temperatures and that objectionable side reactions are reduced and cleaner products are produced.
• U .S. Patent 3,256,241 is directed to the use of alkyl titanates in both an ester interchange and polycondensation reaction to prepare polyesters suitable as fibres.
• U.S. Patent 3,803,275 is directed to a method for preparing containers from poly(ethylene terephthalate).
• This patent discusses the problems of manufacture in processing poly(ethylene terephthalate)resins for films or containers and discloses an elaborate process for preparing a shaped article from a poly(ethylene terephthalate) resin, based on the limited amount of time properly to cool the formed article in order to avoid the formation of crystalline poly(ethylene terephthalate)in the formed article.
• U.S.Patent 3,745, 150 is concerned with a container prepared from poly(ethylene terephthalate) and teaches that the poly(ethylene terephthalate) becomes crystalline when it cools and, unless special precautions and procedures are used, the container contains a substantial amount of crystalline poly(ethylene terephthalate) rendering it unsuitable for many uses.
• the disclosure is based upon the accepted crystallization time, when preparing a formed article, and discloses elaborate procedures for assuring that the formed article will contain substantially all amorphous material.
• poly(ethylene terephthalate) films or moulded articles of a controlled degree of whiteness and opacity intermediate between colourless, clear and maximum whiteness and opacity it may be desired to obtain poly(ethylene terephthalate) films or moulded articles of a controlled degree of whiteness and opacity intermediate between colourless, clear and maximum whiteness and opacity.
• the rapid crystallization time rendered such control difficult, if not impossible.
• This invention provides a poly(ethylene terephthalate) resin having an intrinsic viscosity of 0.55 to 0.85/and a crystallization time of at least 90 seconds often more than 150 seconds at a temperature of 200°C.
• This invention also provides a process for preparing such a poly(ethylene terephthalate) resin comprising forming a poly(ethylene terephthalate) prepolymer and poly-condensing said prepolymer at a temperature of from 265°C to 300°C in the presence of from 2 to 20 parts of catalyst metal, in the form of an alkyl titanate, per million parts of polymer product.
• substantially amorphous means that at least 95% by weight of the final product, lacks a crystalline structure.
• the poly(ethylene terephthalate) prepolymer may be formed by an ester interchange reaction or by direct esterification reaction between ethylene glycol and terephthalic acid.
• Such an ester interchange reaction can take place between ethylene glycol and dimethyl terephthalate.
• the reaction is generally conducted under atmospheric pressure and at a temperature of from 160° C to 225°C. During such a reaction, methyl alcohol. is distilled off as a by-product.
• the pressure is generally 1 or 2 atmospheres and the temperature is generally from 220°C to 260°C. During the esterification reaction, water is distilled off.
• esterification catalysts which may be used are zinc acetate, calcium acetate, titanium ethoxide, manganous acetate and antimony oxalate. Suitable esterification catalysts are well known.
• the direct esterification reaction is generally considered complete when no further water is distilled off or the amount of water distilled is about 90% to 95% of the theoretical yield.
• the mole amount of ethylene glycol used for each mole of dimethyl terephthalate or terephthalic acid used will generally vary from 1.8 to 2.2 moles of ethylene glycol per mole of dimethyl terephthalate or terephthalic acid and preferably will be a mole ratio of from 2 to 1.
• the amount of metal-containing catalyst which is used in the ester interchange reaction may vary widely but will generally be from 20 parts to 200 parts of catalyst metal, per million parts of dimethyl terephthalate.
• ester interchange catalysts are manganous acetate, lithium acetate, sodium methylate, magnesium acetate, cobalt acetate, calcium acetate, cobalt dichloride, manganese acetate tetrahydrate, zinc acetate and sodium hydrogen hexabutyloxy titanate.
• the ester interchange reaction is considered complete when, at the temperature of from about 160° to about 225°C., either the amount of methanol distilled from the reaction is about 90 to 95% of the theoretical yield or no further methanol is removed.
• the reaction mixture containing the poly(ethylene terephthalate) prepolymer is polycondensed at a temperature of from 265 o C to 300°C.
• the amount of catalyst used in the polycondensation reaction may vary widely from about 2 parts to about 20 parts, based on the amount of metal present in the catalyst, per million parts of calculated polymer product. It is preferred, however, that from 2 to 16 parts of catalyst, on the aforesaid basis,be used and most preferably from 8 to 12 parts. Although tne amount of catalyst present may exceed 20 parts per million, e.g., 50 parts, unless compensating steps are taken, the resultant resin may be discoloured, usually yellow.
• titanic acid ester may be used as the catalyst.
• catalysts may be mentioned tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate.
• the polycondensation reaction is generally conducted under a vacuum at a pressure of less than one torr.
• the polycondensation reaction is generally considered complete when the reaction product becomes sufficiently thick for example as determined from the amount of power that is required to drive the stirrer which is present in the reaction kettle.
• the resin is removed from the kettle and may then be extruded into ribbons and diced.
• the molecular weight of the resultant resin may be increased by heating the resin to a temperature above its glass transition temperature but below its melting point and passing a stream of an inert gas over the resin or by holding the resin under vacuum for a period of from 8 to 14 hours at a temperature of from 200°C. to 235°C.
• the resultant resin has an intrinsic viscosity of from 0.55 to 0.85 dl/g and preferably from 0.70 to 0.76 dl/g.
• the starting materials may include other acidic comonomers besides dimethyl terephthalate and/or terephthalic acid so that the final product may have up to 2% by weight of / non-poly(ethylene terephthalate)repeating units and the term "poly(ethylene terephthalate) is to be so construed.
• comonomers which may be present in a total amount of up to 2% by weight include diethylene glycol, isophthalic acid, propane-1, 3-diol, butane 1,4-diol, polytetramethylene glyrol, polyethylene glycol, polypropylene glycol, 1,4-hydroxymethylcyclohexane, bibenzoic acid, naphthalene 1,4 or 2,6-dicarboxylic acid, adipic acid, sebacic acid, decene 1, 10 dicarboxylic acid and esters thereof.
• any other comonomers which are included are usually all esters and when the direct esterification route is used, such other comonomers are usually all acids.
• Such other glycols include neopentyl glycol, propylene glycol and butylene glycol.
• the poly(ethylene terephthalate) resin may also be compounded with various additives such as antioxidant stabilizers, ultraviolet light screening agents, extrusion aids, dyes, or pigments and mould release agents for end use.
• additives such as antioxidant stabilizers, ultraviolet light screening agents, extrusion aids, dyes, or pigments and mould release agents for end use.
• Other possible additives are known which must not adversely affect the resin in its intended use.
• Crystallization time is determined using a Perkin Elmer DSC-II differential scanning calorimeter using the following procedure. Approximately 10 milligrams of dried poly(ethylene terephthalate) resin is placed in the sample pan which is then placed in the calorimeter. The sample is heated to 573 0 K and held at that temperature in order to melt the poly(ethylene terephthalate). After 120 seconds at 573°K, the sample is cooled at a rate of 160 K per minute to a final temperature of 473 0 K (200°C.). The exotherm is recorded and the crystallization time is taken as the time from the point that the recorder pen stabilizes on the base line to the time of maximum crystallization exotherm.
• the crystallization time of the resultant resin, measured at 200°C. is 90 seconds.
• Example one The procedure of Example one is repeated nine times with the following variations in addition to those indicated in the Table following.
• Example 5 the ester interchange catalyst is used in an amount such that 50 parts of manganese and 40 parts of cobalt, both per million parts of final product, are used. In addition, 112 parts of phosphorous, as phosphorous acid is used.
• dimethyl isophthalate is present in an amount such that the final product contains up to 2%, based on the repeating units of said resin, of the dimethyl isophthalate moiety. Additionally, the ester interchange catalyst is used in an amount such that 40 parts of manganese and 60 parts of cobalt, both per million parts of final product, are present.
• Example 9 the ester interchange catalyst is present in an amount such that 70 parts of manganese and 20 parts of cobalt, both per million parts of final product, are present.
• Example 9 is a comparative example wherein a different polycondensation catalyst is used and demonstrates the effect of the different catalyst on the crystallization time of the final resin.
• Example 10 a coglycol, neopentyl glycol, is used in an amount such that the final product has up to 2% of its repeating units derived from the coglycol.
• Intrinsic viscosity [N] is then calculated according to the formula:

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyesters Or Polycarbonates (AREA)

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Cited By (3)

Citations (6)

• 1981
  • 1981-08-26 EP EP81303893A patent/EP0047608A1/fr not_active Withdrawn
  • 1981-09-07 JP JP13987781A patent/JPS5778418A/ja active Pending

Patent Citations (7)

Non-Patent Citations (2)

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